The present invention relates to a spindlehead for tools which may be inserted into a tool disk with tool carriers provided for this purpose, and to chucking means for the spindle holding the shank of the tool in a second end section adjoining the first end section. The first end section is rotatably mounted in the spindlehead housing with a spindle bearing. A coolant feed line extends at least in part in the spindlehead housing. Coolant is transferred over at least one coolant channel which represents an internal coolant feed line for the tool involved. The internal coolant feed line is separated from a drainage channel by a sealing device with a throttle point. The sealing device has at least one sealing ring which encloses the spindle.
DE 195 16 986 C2 discloses a spindlehead, for tools which may be inserted into a tool disk of a turret with tool insertion holes as specified in DIN 69880 [German Industrial Standard 69880] (especially Part 6, March 2000, pages 2 and 4).
In addition, coolant transfer occurs in a spindlehead cover provided on the tool side in which an annular groove is provided. A coolant feed channel discharges into the groove. Through that channel, coolant is delivered internally for a particular tool. In the conventional solution, the coolant transfer point is situated upstream from the spindle bearing. The annular groove is open up to the first end section and is provided with a connecting channel. One end of the connecting channel discharges into the annular zone of the first end zone surface oriented toward the annular groove. The other end of the connecting channel discharges into a chucking means space of the spindle with which the inlet opening provided in the shank end of the coolant channel extending through the tool communicates. The annular groove itself is sealed from the exterior by an external split seal and from the interior in the direction of the spindle bearing by an internal split seal. Both the external and the internal split seals are bounded by the external surface of the spindle and the internal surface of the spindlehead. This arrangement results in a creation of a spindlehead for tools with internal coolant feed which takes up little installation space on the tool disk. In addition, reliable sealing is ensured which in no way exposes the spindle bearing to damage by the coolant.
DE 38 24 427 A1 discloses a machine tool with a spindlehead carrier and a spindlehead mounted on this carrier and provided with a spindle. The drive shaft mounted in the spindlehead carrier is connected to the spindle by gears, bevel gears in particular. In the area of the gears, an oil circulation space for lubrication of the gears is provided. The oil circulation space is sealed from the stationary component of the spindlehead by sealing elements. Compressed air is applied by compressed air feed lines feeding compressed air via throttling ports to the front sealing surfaces of the sealing elements operating in conjunction with opposite rotating sealing surfaces. The pressure relationships and the line cross-sections are selected such that a sealing gap is present for the purpose of contact-free sealing between the rotating opposite sealing surfaces and the sealing surfaces of the sealing elements. Hence, the conventional solution achieves oil lubrication through an oil circulation space. Escape of oil at an undesirable location is prevented by sealing of the oil circulation space by compressed air. The compressed air introduced into the oil circulation space and the resulting excess pressure make certain that the oil lubricant will reach the gears to be lubricated. The oil circulation space is then filled with an oil and air mixture and the gears need not operate entirely in oil. The sealing gap in question of the respective sealing elements thus serves the purpose of delivery of lubricant for the gearing referred to.
DE 42 26 922 A1 discloses a generic spindlehead having a coolant device for supply of the respective boring and/or cutting tools with coolant and/or lubricant. The spindle is provided with an axial channel element fed via an opening in a stationary feed device for transfer of the coolant and/or lubricant to the tool/working area. The feed device and the spindle mesh to form a split seal coaxially. In the conventional solution, leaks through the split seal are removed by a pressure relief space so as to flow to the exterior (virtually free of pressure). This pressure relief space is sealed from, the spindlehead housing downstream on the bearing side by another split seal. The coolant feed proper further requires delivery of compressed air for the conventional sealing solution. Compressed air is applied to this split seal to support the sealing effect. The respective conventional solution in this embodiment requires much installation space and is cost-intensive in application and in maintenance.
Objects of the present invention are to provide and optimize a spindlehead, and in particular to increase the accuracy of machining with the tool, achieve better use of available installation space, and lower manufacturing costs an d potential maintenance costs.
The foregoing objects are basically obtained according to the present invention by the sealing ring being guided coaxially and longitudinally so as to be displaceable relative to the spindle axis in the spindlehead housing. After longitudinal displacement into a sealing position, the sealing ring separates the interior coolant feed, including a prescribable leakage amount, from the parts of the drainage channel to be associated with the feed. The interior coolant feed from the area of the pressurized means for the shank of the tool may be transferred back in the opposite direction into the spindlehead housing. The spindle bearing itself can then move further forward into the area of the pressurized means, so that the tool is better guided and supported by the spindle carrier and the spindle bearing. This situation definitely favors machining accuracy.
Since the internal coolant feed may now take place exclusively centrally by way of the sealing device and along the longitudinal axis of the spindle, installation space is conserved. In addition, a cost-effective solution is achieved, one which also noticeably lowers any subsequent maintenance costs.
Since the respective sealing ring of the sealing device may be displaced longitudinally, a dynamic sealing is achieved which is automatically adapted to prescribed machining situations such as delivery of coolant lubricants, speed of spindle unit, etc. Because of the floating layout of the respective sealing ring, sealing is effected as a function of the pressure relationships and the quantity of coolant to be supplied. As a result, the optionally aggressive coolant cannot reach places which might be damaged by it, ones in the form of the spindle bearing, for example.
In a preferred embodiment of the spindlehead of the present invention, the sealing device has two sealing rings whose sealing surfaces are positioned opposite and against the spindlehead housing with their front sides facing away from each other. This permits a layout in which the respective sealing ring is guided over its external circumference along the spindlehead housing and can slide, generating little friction, on a cushion of coolant produces internal feed of coolant through the spacing between the respective sealing ring and spindle. Sealing with a prescribed amount of leakage can then be effected by way of the front side of the sealing ring in question facing the spindlehead housing.
In another preferred embodiment of the spindlehead of the present invention, the two sealing rings are connected to the coolant feed line on their sides facing each other. An optional axial connection for internal coolant feed is present in the spindle. This arrangement results in good control of the sealing rings by the coolant, and reduces the need for installation space as a result of intervention of the internal coolant feed in the connection option. Space is thereby conserved.
In an especially preferred embodiment of the spindlehead of the present invention, each sealing ring has flexible sealing means on its external circumference. Such means rest on the spindlehead housing, and exert a restoring force on the sealing rings tending to keep the rings together. Dry operation of the spindlehead without coolant is also possible on the basis of this layout. The two sealing rings are held together and kept at a distance from the driven spindle both axially and radially so that to this extent no harmful friction occurs and the spindle can rotate freely in the spindle bearing.
In another preferred embodiment of the spindlehead of the present invention, the throttling point is in the sealing rings in the form of lubricant pouches. The pouches are mounted spaced at a distance from each other on the limiting surface of the sealing rings to allow passage of coolant to form a leakage point. A small leakage flow of coolant is built up by the lubricant pouches; but this flow is in the form of a pressure cushion such that the rotating spindle moves more or less free of friction inside the sealing rings mounted stationarily in the spindlehead housing. A hydrostatic lubrication is thereby achieved. The respective leakage point discharges preferably into the drainage channel. The damage channel emerges from the spindlehead housing into the open through a longitudinal channel section extending parallel to the longitudinal axis of the spindle.
In a preferred embodiment of the spindlehead of the present invention, the sealing device encloses the spindle on the side facing away from the tool shank, beyond the spindle bearing engaging the first end section. The sealing device is thus mounted between a first and a second end section of the actuatable body of the spindle in the spindlehead housing more or less in a manner so as to conserve space.
In another preferred embodiment of the spindlehead of the present invention, additional seals are present upstream and downstream from the spindle in the longitudinal direction. One seals the spindle from the sealing device. In this way lubrication of the spindle through the leakage points is sealed from the other parts of the spindle bearing. This layout preferably also connects the coolant feed radially from the spindlehead housing to a central supply point to conserve space and ensure dependable coolant supply.